Flat Panel Detector:
Overview-
As part of digital radiography (DR), flat panel detectors (FPDs) are used to convert x-rays into light (indirect conversion) or charge (direct conversion), which is then read out using thin film transistors (TFTs).
With many advantages over X-ray film plates, flat-panel detectors have replaced X-ray film imaging in the modern world.
The flat panel detector has been used in several extraoral imaging devices as well as for medical imaging. It is possible to obtain direct digital imaging of a larger area of the body, including the head, using detectors with matrix areas of less than 100 m2.
Canon X-ray Flat Panel Detector (FPD) uses Quadcel technology to provide excellent X-ray images with high sensitivity, high resolution, and low noise. It features the highest X-ray image quality output while maintaining a low dose to the patient.
Basic Functionality:
FPDs have an array of pixels that are sensitive. Generally, FPDs are rectangular or round. For dental radiography, this can be a few centimeters wide, but for chest imaging, it can be several tens of centimeters wide.
Thousands of pixels are contained in the array. Pixels are square in shape and are tens or hundreds of micrometers in length depending on the spatial resolution needed.
A very short shot of irradiation is administered to the pixel array every time an X-ray image is taken. This irradiation is captured by the pixels and stored until it is read out. Pixels consist of photodiodes and switches. In terms of generating electrical charge from X-ray imaging, the photodiode is the basic component. Depending on the method used, either direct or indirect conversion can be used.
Pixels also contain switches, which are typically Thin-Film Transistor (TFT) devices, which are used in displays. The latest performance-enhancing technology, Indium Gallium Zinc Oxide (IGZO), can also be implemented as switches for Flat Panel Detectors (FPDs). Over the next few years, this will become more prevalent.
In order to achieve a high-quality image, and therefore a better medical diagnosis, a number of parameters need to be considered in the FPD. Several of these parameters can be influenced by the performance of ROICs and gate drivers. For this reason, high-performance ICs need to be selected. Performance parameters to pay attention to are:
Sensitivity of the detector: In the case of indirect conversion, the scintillator efficiency will also be considered in addition to the quantum efficiency of the photodiodes
Performance parameters:
Spatial resolution:
Pixel size also plays a role in this. Also, ROICs and gate drivers must be designed to match the pitch of the required channels, which is a substantial challenge.
Readout time:
In dynamic applications, such as rendering the full pixel matrix per frame, the number of frames per second must be high. In order to handle these speeds, the ICs need to be fast enough. In the readout phase, line time refers to the time it takes to convert a line.
Image noise:
Consequently, the more noise in an X-ray image, the less detail can be discerned and the more radiation the patient receives to produce clear images. It is expected that the intrinsic noise of the detector should be a small fraction of the noise added by the ICs.
Amount of power consumed:
The effects of this are not only on electricity costs and the environment but also on portable, battery-powered FPDs’ useful operating time and battery costs.